Percutaneous access to the cardiovascular system is used to diagnose, evaluate, and treat a variety of conditions. A typical procedure involves passing a wire guide through an opening in a patient's skin often by way of an introducer sheath, which connects to a vascular structure such as a vein or artery. The wire guide can then be passed through the cardiovascular system to a location of interest within the patient. Once the wire guide has been appropriately positioned, a catheter may be passed into the patient and guided by the wire guide to a location where a procedure is to be performed. Angioplasty, imaging, and the placement of stents, grafts, filters and other devices, are common procedures which are performed according to variations of the above general technique. It is also common to use percutaneous access for the placement of catheters which deliver fluid at an intraluminal treatment site. Devices known as infusion catheters are used to deliver a therapeutic treatment fluid such as a thrombolytic agent to a clot or the like within a vein or artery. A wide variety of infusion catheter designs are known and commercially available. One general class of infusion catheters utilizes a longitudinally extending lumen which connects a supply of therapeutic fluid located outside of the patient with an intraluminal space by way of ports communicating between the lumen and the intraluminal space. Various locations on a patient's body may be used to percutaneously access the cardiovascular system for infusion in this manner. While in some instances a location of interest within the patient can be reached from a nearby access point, in other instances a preferred access point may be relatively farther away. As a result, relatively long infusion catheters are often used, to enable a treatment site within, for example, a patient's torso, to be reached form a relatively remote access point such as the patient's neck or ankle area. One problem with conventional infusion catheters may be a difficulty in supplying fluid uniformly along the catheter infusion length. Various strategies, such as non-uniform distribution of the infusion ports have been suggested to address this challenge, meeting with varying degrees of success. The use of multiple lumens for conveying fluid independently to different sections of a catheter infusion length has also been proposed. Such designs are believed to provide for more uniform infusion than is practicable or possible with certain single lumen designs.
Still other strategies have included the use of specialized ports for supplying the treatment fluid into a body lumen of a patient. Pressure responsive slit designs are well known, in which normally closed slits are positioned along an infusion length of an infusion catheter, and treatment fluid supplied into a lumen connecting with the pressure responsive slits. When a pressure of the treatment fluid exceeds a threshold sufficient to overcome a closing bias of the pressure responsive slits, treatment fluid can begin to flow out of the infusion catheter through the slits and into a body lumen of the patient. Such designs appear to improve over certain conventional port configurations, as the relatively mild pressurization of treatment fluid within the infusion catheter is believed to impart a tendency for fluid pressure within the catheter lumen to more or less equalize prior to commencing infusion. As a result, similar internal pressures prevail along the catheter infusion length and, hence, non-uniformity in flow rate out of the catheter is reduced. While certain of these known designs have seen commercial success, there remains room for improvement both in the practical implementation of infusion procedures and methods by which infusion catheters are made.